1. Field of the Invention
The invention relates to a semiconductor device and a method for preparing the same, and more particularly to a DRAM made of a material of high dielectric constant and including a capacitor using the material, and method for preparing the DRAM.
2. Description of the Related Art
A capacitor must keep its capacitance at a specified degree as cell sizes are reduced following development of DRAMs of higher density. A material of high dielectric constant and a capacitor construction using the material as well as a stacked capacitor of a larger surface area and a thin film dielectric have been researched in this regard. Ta.sub.2 O.sub.5 capacitor dielectric film has been given attention as a thin film dielectric of high dielectric constant. But, the Ta.sub.2 O.sub.5 dielectric film is provided with a lower electrode using a polysilicon film or silicide film (e.g., WSi.sub.2), so that it does naturally have SiO.sub.2 formed at an interface between Ta.sub.2 O.sub.5 and polysilicon, leading to deterioration of a practical dielectric constant of the capacitor.
Also, the Ta.sub.2 O.sub.5 film generally causes high leak current and is difficult to be employed by itself.